Maple Leaf

Prospect, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities As; Bi; Mo; Te
Ore minerals arsenopyrite; bismuthinite; gold; molybdenite
Gangue minerals quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale EA
Quadrangle map, 1:63,360-scale B-6
Latitude 64.4013
Longitude -143.9333
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Maple Leaf prospect is located 2 miles north of Eisenmenger Fork, Goodpaster River; 0.6 mile from the center of section 11, T. 6 S., R. 19 E., of the Fairbanks Meridian. This location is accurate to within 500 feet.

Geologic setting

Geologic description

The Maple Leaf prospect is located in the eastern edge of the Goodpaster Mining District, and it was discovered during regional pan concentrate and stream sediment sampling conducted by Avalon Development Corp. for Evanachan Ltd. in the fall of 2006 (Freeman, 2015).
The primary host rocks at the Maple Leaf prospect are Cretaceous(?) age unfoliated biotite granite and biotite quartz monzonite. These rocks are fine- to medium-grained, equigranular and contain abundant quartz and biotite. There are numerous dikes of the biotite granite-quartz monzonite cutting the gneissic country rocks. Sulfide-bearing auriferous quartz veins are hosted in dikes of this unit. Maple Leaf is structurally bounded by numerous northeast-trending, near-vertical faults, which may control gold mineralization (Freeman, 2015).
Mineralization is characterized by sugary textured quartz veins and locally by vein stockworks of variable orientation associated with intrusive and country rock (gneisses) containing trace to 2 percent sulfides characterized by arsenopyrite +/- bismuthinite +/- molybdenite and, locally, visible gold. Outcrop in the area is limited and solifluction has clearly transported float boulders down slope. Vein widths range from less than 1.0 meter to vein stockworks over 1-3 meters. Large (0.5 by 0.25 meter) boulders containing bismuthinite-bearing veins noted from the prospective area have not yet been traced to their source although, given the topography, the source is likely local (Freeman, 2014).
Samples from work in 2006 of a quartz vein boulder float/train and from stream sediment and pan concentrate samples in surrounding drainages identified a 10 kilometer by 7.0 kilometer area with greater than 100 parts per million (ppm) arsenic stream silt and pan concentrate anomaly. Within this area quartz vein samples interpreted as bedrock or sub-crop returned anomalous gold (from trace up to 12 grams per tonne). Evanachan Ltd. was acquired by Rubicon Minerals in early 2007 and follow up work, including limited diamond drilling (1,105 meters in 4 holes), was conducted in 2007.
Assays of grab rock samples collected in 2007 returned gold values from trace to 19.1 grams per tonne with 19 samples (total 114 rock samples) containing gold in excess of 1.0 gram of gold per tonne with an average of 5.2 grams of gold per tonne. Gold is associated with elevated bismuth (up to 7,700 ppm), tellurium (up to 280 ppm) and variable arsenic (Freeman, 2014).
Geologic map unit (, )
Mineral deposit model Polymetallic veins (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Cretaceous or younger based on age of host rock (Freeman, 2015).
Alteration of deposit Moderate to weak sericite alteration in biotite quartz monzonite adjacent to sugary textured quartz veins, which host the gold mineralization (Freeman, 2015).

Production and reserves

Workings or exploration
The Maple Leaf prospect was discovered during regional pan concentrate and stream sediment sampling conducted by Avalon Development Corp. for Evanachan Ltd. in the fall of 2006. Follow up rock and grab samples were collected that year (Freeman, 2014).
In 2007, Avalon Development managed a diamond core drilling program
for Rubicon on the Maple Leaf prospect. The program included 1,105 meters of drilling in four holes. Drilling beneath surface gold-quartz vein showings intersected weakly anomalous (up to 0.25 gram of gold per tonne over 0.8 meter) but did not intersect vein style mineralization similar to that observed on the surface (Freeman, 2014). Values up to 19 grams of gold per tonne were assayed (Freeman, 2014).
The land was open to mineral entry until staked by Anglo Alaska Gold Corp. in 2011 and assessment-level work has been conducted by Anglo Alaska since 2011 (Freeman, 2014).
Indication of production None
Reserve estimates None.
Production notes None.

Additional comments

According to Freeman (2015), after the 2007 drilling, no other work was conducted on the Maple Leaf prospect and in the fall of 2008, Rubicon dropped the claims covering these prospects. No significant mineral exploration has been conducted on the prospect since that time.



Reporters V.C. Zinno (Alaska Earth Sciences, Inc.), F.H. Wilson (USGS)
Last report date 3/15/2016